The annual mean irrigation input of farmland was 12,000 m3 ha−1, and the annual mean chemical fertilizer input was 1500–1800 kg ha−1 (N:P2O5:K2O = 1:1:1), and farmyard manure (compost heap) was applied at a rate of 15,000–18,000 kg ha−1 at 2–3 year intervals. In the present study, the stalks and main roots of maize and wheat were removed as fuel after harvest, and only a small amount of the residues was returned to the soil.